Pyrotechnic cool gas generation method for inflatable structure

ABSTRACT

The introduction of a generated gas through an oxidizer bed, which, optionally, may also include a coolant.

United States Patent [191 Hamilton [54] PYROTECHNIC COOL GAS GENERATIONMETHOD FOR INFLATABLE STRUCTURE [75] Inventor: Brian K. Hamilton, Utica,Mich.

[73] Assignee: Allied Chemical Corporation, New

York, N.Y.

[22] Filed: Nov. 19, 1973 [21] Appl. No.: 417,453

Related US. Application Data [63] Continuation of Ser. No. 224,525, Feb.8, 1972,

[451 Dec. 30, 1975 [56] References Cited UNITED STATES PATENTS 3,532,35910/1970 Teague et al 280/150 AB 3,647,393 3/1972 Leising et al. 102/39 XPrimary Examiner-Stephen .l. Lechert, Jr. Attorney, Agent, orFirm.lonathan Plaut 57 ABSTRACT The introduction of a generated gasthrough an oxidizer bed, which, optionally, may also include a coolant.

3 Claims, 1 Drawing Figure AIR CUSHION -+1 I I I I I I CARBONATE COOLANT(OPTIONAL) COOLANT PROPELLENT PYROTECHNIC COOL GAS GENERATION METHOD FORINFLATABLE STRUCTURE This is a continuation of application Ser. No.224,525, filed Feb. 8, I972, now abandoned.

BACKGROUND OF THE INVENTION Automobile safety has indicated use of aircushion systems for passenger restraint. Much research and developmenthas recently been carried out in the development of such air cushionsystems both for the protection of passengers, as disclosed for examplein US. patent application Ser. No. 8 I ,947, filed Oct. l9, I970, US.Pat. No. 3,874,059 and for the protection of the driver, as for examplein US. patent application Ser. No. 147,913, filed May 28, I970 now US.Pat. No. 3,787,074. In both the case of the protection of the passengerand the driver, the gas used to fill the protective structure (cushionor bag) may be in part or all generated gas from a combustible material.

It is necessary that the generated gas withstand storage from about 40F.to +220F., ignite rapidly, for example within just a few milliseconds betotally ignited and producing non-toxic gas, and produce gas at arelatively low temperature (less than about 2,000F.) when burned atpressures from I to 20,000 lbs/in. It has been proposed to use a purepyrotechnic gas generator producing a non-toxic gas where the propellantand the oxidizer are mixed, either as a rough grain or as a contractedproduct. It has further been proposed to add to that mixture or to coolthe gas produced from that mixture with a carbonate or other coolant.How ever, such mixtures present problems, as it is extremely difficultto control the rate of burn because of the mix of ingredients, and withthe mixture of ingredients the burning occurs at a relatively highpressure. Furthermore, the mixture of propellant and oxidizer results instabilizing problems connected to ambient temperature changes andstorage conditions.

BRIEF SUMMARY OF INVENTION Therefore, according to this invention a gasgenerating, solid propellant grain which may be of a conventional type,such as a PVC propellant, is utilized to product a gas. That gas is thenpassed through an oxidizer, such as a metal chlorate or perchlorate, inthe form of a porous bed. Optionally, a coolant, such as a carbonate,may be added to the oxidizer to further cool the generated gas. Theproducts produced by such treatment of the produced gas from a PVCpropellant include approximately 10 percent carbon dioxide (C0,), l0percent water vapor and 80 percent oxygen, with substantially no toxiccarbon monoxide (CO) produced. The temperature of the gas supplied as aresult of oxidation, without the use of the carbonate coolant, is below2000F. and as low as I400F. or lower.

DESCRIPTION OF INVENTION In the preferred embodiment of this invention,the combustible propellant is made up ofa PVC propellant grain, thoughthe propellant may be any standard propellant which will producenon-toxic gas for use in filling an air cushion assembly. In thedrawing, which shows a schematic flow of the invention, propellant isshown as burning and then passing through a porous bed of oxidizer.

The porous bed of oxidizer may be formed of any metal chlorate orperchlorate, preferably potassium chlorate (KCIO and/or potassiumperchlorate (KCIOJ. The gas from the burning propellant passing throughthe oxidizer undergoes extreme oxidation, and the resultant products asa result of this oxidation are carbon dioxide (CO water and oxygen, withsubstantially no carbon monoxide (CO) produced. The porous bed mayinclude a coolant such as metal carbonate and/or bicarbonate to furtherlower the temperature of the generated gas before it passes, as shown inthe schematic, into the air cushion. Furthermore, optionally, the gasleaving the porous bed can also be further cooled by mechanical heatexchange, such as passing it over metal wire, chain, sintered or loosemetal particles, etc., if desired, before passing it into the aircushion.

The solid propellant can be used as an extruded, cast, or mechanicallycompacted (pressed) grain.

The coolant is preferably a carbonate, such as magnesium carbonateand/or sodium carbonate which will absorb heat as a result ofdecomposition from the generated gas.

In one specific example, a PVC propellant grain commercially known asArcite 497C of the Atlantic Research Corporation was burned and theproduced gas introduced into a porous bed of recrystallized potassiumchlorate crystals of an average of about 500 microns diameter. Noseparate carbonate coolant was used. A temperature of about I400F. ofthe resultant gas directed to the air cushion was achieved. About l0percent carbon dioxide (CO l0pereent water vapor, and percent oxygen wasproduced as the gas filling the air cushion. Substantially no toxiccarbon monoxide was produced. Of course, the addition of a chemicalcoolant, such as a carbonate which will absorb heat as a result of itscontact with the generated gas in the porous bed, or thereafter, ifdesired, would further lower the temperature of the generated gas.

By the process indicated, the burn of the propellant can be controlled,as previously discussed, because there is no intermixture of theoxidizer or the oxidizer and the coolant with the burning propellantgrain. Furthermore, without the mixture of oxidizer and propellant,lower pressures at which the propellant burns are attainable for anequal amount of gas produced per given amount of time. Furthermore, as aresult of the lack of such intermixture, the storability of the productis made more favorable.

It is understood that the above-described example and generaldescriptive matter is merely illustrative of the invention and not meantto limit said invention, except as such invention is within the scope ofthe following claims.

I claim:

I. A method of filling an air cushion assembly with a generated gaswithout the production of carbon monoxide and at a temperature less thanabout 2000 F., comprising burning a propellant grain to generate gas,passing said generated gas through a porous bed of oxidizer and coolant,further cooling said gas by mechanical heat exchange with a heatexchange surface after passing the gas through the bed, further treatingthe oxidized gas emerged from the porous bed with a separate coolant,and directing the generatedgas to an air cushion assembly.

2. A method as set forth in claim I, said coolant in each occurrenceselected from a class consisting of 4 chlorate, metal perchlorate and acombination of the two.

1. A METHOD OF FILLING AN AIR CUSHION ASSEMBLY WITH A GENERATED GASWITHOUT THE PRODUCTION OF CARBON MONOXIDE AND AT A TEMPERATURE LESS THANABOUT 2000*F., COMPRISING BURNING A PROPELLANT GRAIN TO GENERATE GAS,PASSING SAID GENERATED GAS THROUGH A POROUS BED OF OXIDIZER AND COOLANT,FURTHER COOLING SAID GAS BY MECHANICAL HEAT EXCHANGE WITH A HEATEXCHANGE SURFACE AFTER PASSING THE GAS THROUGH THE BED, FURTHER TREATINGTHE OXIDIZED GAS EMERGED FROM THE POROUS BED WITH A SEPARATE COOLANT,AND DIRECTING THE GENERATED GAS TO AN AIR CUSHION ASSEMBLY.
 2. A methodas set forth in claim 1, said coolant in each occurrence selected from aclass consisting of magnesium carbonate, sodium carbonate, or acombination of the two.
 3. A method as set forth in claim 1, said porousbed of oxidizer selected from the class consisting of a metal chlorate,metal perchlorate and a combination of the two.